Measuring device for determining the characteristics and the level of a brake fluid in a motor vehicle

ABSTRACT

Disclosed is a measuring device ( 1 ) for determining one or more characteristics of a fluid or the level of this fluid in a reservoir ( 8 ). In particular, the device is utilized in the brake fluid reservoir of a motor vehicle brake system that may be electronically controlled. The device includes an integrated measuring electronic system ( 2 ), a sensor device ( 4 ), an electric supply line ( 18, 26 ), and an electric connecting line ( 9 ).

BACKGROUND OF THE INVENTION

The present invention relates to a measuring device for determining thecharacteristic(s) of a fluid and/or the filling level of this fluid in areservoir (8) receiving the fluid, which is arranged in particular inthe brake fluid reservoir of a motor vehicle brake system that ispreferably controlled electronically.

Different methods and devices for determining the moisture content in abrake fluid are known in the art. In some methods, the quality of thehygroscopic brake fluid, in particular the water contents, is determinedby determining the boiling point of the fluid, for example.

The device for determining the quality by using the boiling temperatureas known from EP 0 513 004 is so designed that the sensor element isconfigured as at least one linear conductor, e.g. a wire. Apparatusfeatures which are directed to an arrangement in a brake fluid reservoircannot be taken from this publication.

The device described in EP 0 289 499 B1 concerns a brake fluid testingappliance where a bubble boiling zone is produced in a measuring cell.The device concerned is not appropriate for being installed into a motorvehicle because it is designed as an appliance.

The device which is described rather schematically in DE 101 47 804 A1comprises a sensor element and a heating element in a cylinder-shapedmeasuring chamber. It does not disclose a special embodiment which wouldrender the sensor apt for use in a brake fluid reservoir.

DE 197 41 892 C2 additionally discloses in terms of principle how tomeasure the filling level in a brake fluid reservoir apart fromdetermining the quality of the brake fluid. DE 197 41 892 C2 mainlydescribes a measuring method. A measuring device for implementing themethod is not disclosed.

Hence, it remains to be stated that the concrete constructive featuresof a measuring device which can be employed reliably in the motorvehicle and can be manufactured at low cost has so far not become knownfrom the prior art.

SUMMARY OF THE INVENTION

In view of the above, the invention has for its objective to disclose adevice for implementing the principally per se known measuring methods,which can be produced at low cost and satisfies the existing and futurerequirements in car making.

According to the invention, this object is achieved by luding ameasuring electronic system, a sensor connected to the measuringelectronic system, an electric supply line connecting the measuringelectronic system and the sensor device, and an electric connecting lineproviding a connection between the measuring device and an electroniccontrol unit for transmissiting the sensor signals.

A special feature of the measuring device of the invention involves thatthe measuring electronic system is integrated in the measuring device.This arrangement renders it possible to avoid electrically shielding theelectric connecting line by which the measuring device can be connectedto an electronic control unit for the transmission of sensor signals.Further, important advantages are achieved in terms of the reliabilityand the manufacturing costs of the sensor.

The favorable possibility of manufacturing the measuring device of theinvention as a plug-in cartridge allows realizing different installationpositions in compliance with the individual wishes of the car makers.

Further preferred embodiments can be seen in the following descriptionof the Figures.

The invention will be explained in detail in the following by way ofexamples.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows an example for a measuring device which is attached in thereservoir cover;

FIGS. 2, 3 show examples for alternative places of installation of themeasuring device;

FIG. 4 shows another example for a measuring device according to theinvention;

FIG. 5 shows an example for a measuring device with a shaped part forsealing that is integrated into a reservoir cover, and;

FIG. 6 shows an example for a measuring device with sealing rings thatcan be screwed into the reservoir.

DETAILED DESCRIPTION OF THE DRAWINGS

Measuring device 1 comprises an integrated evaluating electronic system2 in FIG. 1. The electronic components of the measuring electronicsystem 2 are arranged on a component carrier. It is a special feature ofthe measuring device 1 that the measuring electronic system 2 isintegrated into the measuring device 1. The integration of the measuringdevice achieves a number of advantages. Thus, the possible signalamplification e.g. obviates the need for an electric shielding of thesensor cable. Further, the measuring device 1 does not comprise movableparts. The connection of the printed circuit board is done by way ofplane conducting tracks 26 which can be produced using a punching frame.However, a conductively coated foil material may also be concerned,which offers the advantage of enhanced elasticity. The housing part ofthe measuring device is configured in general like a cartridge andincludes in the area of the sensor elements a partly permeable opening11 through which the fluid can enter into the interior of the housingpart. This opening is e.g. closed by a filter 10. An appeased chamber 12is hereby produced after the sensor has immersed into the brake fluid23, providing a suitable measuring volume for the sensor 13. In thesimplest case, however, a simple recess in the wall of the measuringdevice is concerned, if it ensures the desired extent of fluid exchangebetween the reservoir and the measuring chamber. The housing part canhave one or more additional ventilation apertures 14. The measuringdevice is rotatably mounted in the cover 7 of a brake fluid reservoir 8so that connecting lines 9 which extend from the engine compartment tothe outside of the measuring device, and e.g. lead to the ECU of anelectronic brake system, can be connected more easily in the desireddirection. The device includes a bottom housing part for the sensorelement(s) and a top housing part, sealed therefrom, for theelectronics. The area of the electronics 3 and the area of the sensorsystem 4 are hermetically isolated from each other by means of aseparating element 5. The housing parts can be interconnected inoperative manner in a per se known fashion, preferably by means of acatch 6. A molecular bond is also feasible.

In FIG. 2, the measuring device is connected to the wall of the brakefluid reservoir. This is easily possible because the measuring device isdesigned as a plug-in cartridge.

In FIG. 3, two measuring devices are illustrated in a horizontal and avertical arrangement to show different mounting positions. The overalllength of the illustrated multi-part housing of the measuring device canbe adapted to the respective reservoir shape depending on the type ofvehicle so that a sufficiently deep immersion of the sensor into thebrake fluid is safeguarded. Appropriate seals are used to seal thehousing parts in relation to each other in such a way that displacementof the housing parts in each other is possible. It is preferred that thehousing parts are manufactured in the shape of cylinders, with theoutside housing part 15 having a diameter slightly larger than thediameter of the inside housing part 16 which can be slipped into theoutside housing part 15. The housing part containing the electronics ishermetically isolated from the housing part containing the measuringelements. A sealed passage for the electric lines is provided in thearea of the hermetic sealing. Glass 21 can preferably be provided forthe sealing. Alternatively, electric connecting elements such as plugs,contacts, and like elements, can be provided in this area.

In FIG. 4, the electric lines which connect the measuring electronicsystem to the area of the sensor system 4 in the bottom housing part 17are configured as flexible lines 18 which, compared to rigid lines,exhibit the advantage that they cannot be damaged when the bottomhousing part 17, being hermetically sealed, is displaced for the purposeof length variation. Alternatively, the flexible lines can be simpleinsulated wires. In addition, the fluid reservoir includes one or moreopenings 19 in the area of the housing and/or the closure forventilation of the reservoir, the opening(s) being preferably closed bya textile membrane 20 such as a breathable textile strip made ofGoreTex®. The ventilation arrangement described hereinabove can beshaped at the housing of the measuring device. The measuring device 1 inwhole can be shifted in a longitudinal direction A within the mountingsupport arranged in the cover. Further, the plug cap 24 including theelectronics can be turned in the cover about axis A by a defined angularrange in order to permit connection of an angled-off plug 25 which isconnected to line 9 in different directions.

FIG. 5 shows another possibility of integrating a brake fluid qualitysensor into a reservoir cover. According to FIG. 5, the sensor isintegrated into a series reservoir cover of a standard brake fluidreservoir, in such a way that there is also a venting arrangement in thecover. The outside housing (sensor carrier) is a shaped part whichaccommodates all single parts of the sensor such as sensor head,electrode, electronics and seal for the separation of electronics andsensor elements (temperature feeler and heating element). Inserted intothe top part of the sensor, in the area of the electronics, is a shapedpart accommodating the electronics and, additionally, having sealingqualities in relation to the sensor electrodes. The integral shaped partmade of an elastomer bears against the walls in the area of theelectronics and reliably seals the electronic component in the area ofthe hermetic isolation between electronics and electrodes. In the areawhere the cover is pressed on, an annular washer 34 for sealing thereservoir is placed below an annular sensor abutment collar 28. Towardsthe engine compartment, the electronics is sealed by a plug extension 27which guides the contacts 29 leading from the sensor plug 30 to theelectronics.

FIG. 6 a) shows a separate, lowered reservoir 33 with a quality sensorthat is connected to a separated smaller filling reservoir 32 by way ofa connecting line 31. Cover 7′ is arranged at the filling reservoir 32for filling the brake fluid.

The quality sensor in FIG. 6 b), shown in a cross-sectional view,displays a sensor similar to FIG. 5, with the differences that sealingbetween the electronics and sensor elements is done by means of ringseals, and a separate sealing ring is provided in each case for sealingtowards the sensor head with the quality electrode and towards theelectrode for the filling level. When the venting arrangement in thearea of the cover as illustrated in FIG. 5 is dispensed with, there isthe possibility of using the quality sensor in the separated reservoirarrangement illustrated in FIG. 6 a).

1-12. (canceled)
 13. A measuring device (1) for determining at least ofone or more characteristics of a fluid and a level of the fluid in areservoir (8) receiving the fluid, which is arranged in a brake fluidreservoir of a motor vehicle brake system that is controlledelectronically, the device comprising: a measuring electronic system (2)integrated into the measuring device; a sensor device (4) which isconnected to the measuring electronic system in an electricallyconductive fashion and used to determine at least one of the fluidcharacteristics and to determine the filling level of the fluid in thereservoir receiving the fluid, an electric supply line (18, 26)providing an electric connection between the measuring electronic systemand the sensor device, and an electric connecting line (9) providing aconnection between the measuring device and an electronic control unitfor transmission of the sensor signals.
 14. A measuring device accordingto claim 12, wherein the measuring device includes two or multi-partseparable housing parts being configured as a cartridge, and at leastone of the housing parts is provided with an area that is partlypermeable for the fluid or with an opening which presets a defined flowresistance.
 15. A measuring device according to claim 12, wherein insidethe measuring device there is a zone of separation being used to protectthe electronics against the brake fluid, with a result that inparticular the area of the device is hermetically closed in which theelectronics is accommodated.
 16. A measuring device according to claim15, wherein the zone of separation is arranged in the area where thehousing parts are separated.
 17. A measuring device according to claim12, wherein the electric supply line is formed of wires or planeconductors which are led in a seal-tight manner especially through thezone of separation.
 18. A measuring device according to claim 12,wherein the device is assembled of several parts and can be modified interms of length in order to adapt to various reservoir shapes, or atleast the outside housing is shaped integrally of one material.
 19. Ameasuring device according to claim 12, wherein the measuring device ismounted at the top housing part (21) or the cover (7) or into the wallor into the bottom of the reservoir.
 20. A measuring device according toclaim 19, wherein the measuring device (1) is fixed in an area of thereservoir wall or the reservoir cover and is displaced axially in thedirection of the longitudinal axis of the measuring device for theadjustment in length, or can be turned by a minimum angle about thelongitudinal axis in relation to the reservoir or the cover.
 21. Ameasuring device according to claim 12, wherein the device comprises aplug cap (24) for connection of a plug (25) for the electric connectingline (9), in which in particular the measuring electronic system isattached, and the plug cap is displaceable or can be turned by a minimumangle about the longitudinal axis in relation to the reservoir or thecover.
 22. A measuring device according to claim 12, wherein sealing ofthe electronics and the sensor area is provided by a shaped part whichbears from inside against the housing wall of the electronics area inlarge parts in a form-fit manner, and the shaped part is an integralelastic seal in particular, or sealing is performed by at least oneelastic sealing ring.
 23. A measuring device according to claim 12,wherein a venting arrangement is provided in the sealing area of thecover.
 24. A measuring device according to claim 12, wherein theelectronics area is sealed towards the engine compartment by way of aplug extension (27) which additionally comprises a connecting plug (30)for the sensor connecting cable.